PURPOSE: To reduce the fluctuations in the angle of inclination of interference fringes and obtain good quality reproduced information by so radiating a hologram that spherical object waves and spherical waves for reference have a nearly equal angle of inclination with respect to the normal of the hologram disc.
CONSTITUTION: Laser beam from a light source 8 is focused at the point S' by collimator lenses 9a, 9b, condenser lens 10, after which it is diverged as spherical waves for reference. Laser beam from a light source 3 is focused at the point S, after which it is diverged as object spherical waves. The optical axis B5 and B2 of both waves have the same angle of inclination with respect to the normal N1 of the surface of a hologram disc 1. Similarly the optical axis B4 and B1, B6 and B3 have nearly the same angles of inclinations with respect to the normal N1. Hence, the interference fringes formed on the hologram by the radiation of the object spherical waves and spherical waves for reference become parallel with respect to the thickness direction of the hologram and even if the hologram thickness fluctuates, the fluctuations in the angle of inclination of the interference fringes become slight.
IKEDA HIROYUKI
MATSUMOTO SEIKICHI
